[PATCH] D136015: [InstCombine] Fold series of instructions into mull
Allen zhong via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sat Oct 15 05:01:17 PDT 2022
Allen created this revision.
Allen added reviewers: spatel, efriedma, bcl5980, RKSimon, nikic.
Herald added a subscriber: hiraditya.
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Allen requested review of this revision.
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Herald added a subscriber: llvm-commits.
The following sequence should be folded into in0 * in1
In0Lo = in0 & 0xffffffff; In0Hi = in0 >> 32;
In1Lo = in1 & 0xffffffff; In1Hi = in1 >> 32;
m01 = In1Hi * In0Lo; m10 = In1Lo * In0Hi; m00 = In1Lo * In0Lo;
addc = m01 + m10;
ResLo = m00 + (addc >> 32);
https://reviews.llvm.org/D136015
Files:
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
llvm/lib/Transforms/InstCombine/InstCombineInternal.h
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
llvm/test/Transforms/InstCombine/mul.ll
Index: llvm/test/Transforms/InstCombine/mul.ll
===================================================================
--- llvm/test/Transforms/InstCombine/mul.ll
+++ llvm/test/Transforms/InstCombine/mul.ll
@@ -1574,3 +1574,21 @@
%r = mul i32 %zx, -16777216 ; -1 << 24
ret i32 %r
}
+
+define i64 @mul64_low(i64 noundef %in0, i64 noundef %in1) {
+; CHECK-LABEL: @mul64_low(
+; CHECK-NEXT: [[TMP1:%.*]] = mul i64 [[IN0:%.*]], [[IN1:%.*]]
+; CHECK-NEXT: ret i64 [[TMP1]]
+;
+ %In0Lo = and i64 %in0, 4294967295
+ %In0Hi = lshr i64 %in0, 32
+ %In1Lo = and i64 %in1, 4294967295
+ %In1Hi = lshr i64 %in1, 32
+ %m10 = mul i64 %In1Hi, %In0Lo
+ %m01 = mul i64 %In1Lo, %In0Hi
+ %m00 = mul i64 %In1Lo, %In0Lo
+ %addc = add i64 %m10, %m01
+ %shl = shl i64 %addc, 32
+ %addc9 = add i64 %shl, %m00
+ ret i64 %addc9
+}
Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -852,6 +852,35 @@
return SimplifySelectsFeedingBinaryOp(I, LHS, RHS);
}
+Value *InstCombinerImpl::SimplifyMull(BinaryOperator &I) {
+ if (!(I.getType()->isIntegerTy() && I.getType()->getIntegerBitWidth() == 64))
+ return nullptr;
+
+ Value *In0, *In1;
+ Value *M01, *M10, *M00, *Addc;
+
+ // addc = m01 + m10;
+ // ResLo = m00 + (addc >> 32);
+ bool IsMulLow = match(&I, m_c_Add(m_Value(M00),
+ m_Shl(m_Value(Addc), m_SpecificInt(32)))) &&
+ match(Addc, m_c_Add(m_Value(M01), m_Value(M10)));
+
+ // In0Lo = in0 & 0xffffffff; In0Hi = in0 >> 32;
+ // In1Lo = in1 & 0xffffffff; In1Hi = in1 >> 32;
+ // m01 = In1Hi * In0Lo; m10 = In1Lo * In0Hi; m00 = In1Lo * In0Lo;
+ if (IsMulLow &&
+ match(M00, m_c_Mul(m_c_And(m_Value(In1), m_SpecificInt(4294967295)),
+ m_c_And(m_Value(In0), m_SpecificInt(4294967295)))) &&
+ match(M01, m_c_Mul(m_LShr(m_Specific(In1), m_SpecificInt(32)),
+ m_Specific(In0))) &&
+ match(M10, m_c_Mul(m_LShr(m_Specific(In0), m_SpecificInt(32)),
+ m_Specific(In1)))) {
+ return Builder.CreateMul(In0, In1);
+ }
+
+ return nullptr;
+}
+
Value *InstCombinerImpl::SimplifySelectsFeedingBinaryOp(BinaryOperator &I,
Value *LHS,
Value *RHS) {
Index: llvm/lib/Transforms/InstCombine/InstCombineInternal.h
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -546,6 +546,9 @@
/// value, or null if it didn't simplify.
Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
+ /// Tries to simplify a few sequence operations into MULL
+ Value *SimplifyMull(BinaryOperator &I);
+
/// Tries to simplify add operations using the definition of remainder.
///
/// The definition of remainder is X % C = X - (X / C ) * C. The add
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1286,6 +1286,9 @@
if (Value *V = SimplifyUsingDistributiveLaws(I))
return replaceInstUsesWith(I, V);
+ if (Value *V = SimplifyMull(I))
+ return replaceInstUsesWith(I, V);
+
if (Instruction *R = factorizeMathWithShlOps(I, Builder))
return R;
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